RFR: 8321139: jlink's man page does not document the --compress option correctly

[Ana Maria Mihalceanu]

This PR looks into updating the content of `--compress` option and plugin of `jlink`:

- Updates the `--compress` option description and warns that previous compression levels are deprecated to be removed in a future release.
- Updates the `--plugin` option description and warns that previous compression levels are deprecated to be removed in a future release.

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Commit messages:
 - Update compression level explanation from jlink man page.

Changes: https://git.openjdk.org/jdk/pull/28359/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28359&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321139
  Stats: 14 lines in 1 file changed: 7 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/28359.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28359/head:pull/28359

PR: https://git.openjdk.org/jdk/pull/28359